This invention relates to a system for detecting and indicating various malfunctions in electrically operated apparatus of the type normally found in manufacturing facilities. More specifically, this invention relates to a system which displays and isolates the source of abnormal operating conditions in such apparatus.
It is common for electrical apparatus used in manufacturing facilities, such as heaters or drying ovens, to include a variety of sensors to monitor various operating conditions or parameters. These parameters include, for example, stack temperatures, stack and fuel pressures, and fan operation. If a value of a particular parameter goes outside a predetermined safe range of values, the sensor opens a corresponding switch in the power supply control circuit thereby to open a main contactor and deenergize the apparatus.
Commonly a facility may have several pieces of this apparatus distributed throughout a large area and each piece may have many such sensors associated with it. Moreover, this apparatus often operates without anyone in attendance. When a sensor does turn off an oven, a monitoring system should indicate which sensor, or group of related sensors, monitored the abnormal condition. Sometimes the abnormal condition is intermittent, so it is desirable that any such system indicates the sensor or group of sensors which turns the apparatus off. Such isolation reduces overall operating costs because actual repair times are reduced by minimizing the time necessary to diagnose the problem.
There are diverse detection and indication systems for connection to such apparatus. In one, a transformer connects to a set of switch contacts and to an indicator circuit. When a switch opens in response to a condition, it energizes the corresponding transformer and indicator circuit.
In another system adopted for detecting ground or similar faults in a cable, a fault causes an intermittent high current. A reed switch and photoelectric latching circuit energizes a lamp thereby to indicate a fault condition. If a number of these indicators are juxtaposed to the cable, all lamps on one side of the fault will be lit thereby simplifying the fault location.
These prior systems are somewhat complex so they tend to be expensive because the transformers and latching circuits are duplicated at each sensor.
Consequently, it is an object of this invention to provide a system for isolating malfunctions in complex electrical apparatus.
It is another object of this invention to provide an inexpensive and reliable means for monitoring the operation of plant equipment.